Deemed Undertaking. Amyotrophic Lateral Sclerosis Society of Essex County v. Windsor (City)
In Amyotrophic Lateral Sclerosis Society of Essex County v. Windsor (City) (Ont CA, 2019) the Court of Appeal considered the deemed undertaking rule:
 The core purpose of the deemed undertaking rule is to protect the use to which the compelled production of a party’s private information can be put: Goodman v. Rossi (1995), 1995 CanLII 1888 (ON CA), 24 O.R. (3d) 359 (C.A.); Juman v. Doucette, 2008 SCC 8,  1 SCR 157. The opt-out information is not captured by that purpose. Rather, the opt-out information is information that relates to the identities of the class members who have agreed to be bound by the determinations made in the context of the class proceedings.
 Courts in Canada operate on the openness principle. A person who chooses to commence a court proceeding must do so publicly, subject only to exceptional circumstances where a pseudonym or initials may be used: C.G. v. Ontario (Health Insurance Plan General Manager), 2014 ONSC 5392, 327 O.A.C. 53 (Div. Ct.), at para. 7. The overarching principle applicable to all court proceedings is that the public is entitled to know what proceedings are commenced in our courts, along with the particulars of those proceedings, and whose rights are being submitted for adjudication. Any member of the public is entitled to have access to the court file, and to review all of the material that is filed with the court. In the same way, a defendant is entitled to know who is using the court process to advance a claim against it.
 The respondents, and the Divisional Court, rely on my endorsement in Markle v. Toronto (City),  O.J. No. 3024(S.C.J.) in support of their position. With respect, both mischaracterize my decision along with the nature of the information that was involved. In Markle, the information sought by the representative plaintiff was the private information of the City of Toronto. It was a list of the names and addresses of individuals who had been employed by, but were now retired from, the City. If the action proceeded to discovery, it would have been appropriate for counsel for the representative plaintiff to ask the City’s representative for a list of the retired persons whose claims would be covered by the class action. This request would be consistent with the requirement that rested on the City as a party, by virtue of s. 5(3) of the CPA, to provide its best information on the number of members of the proposed class as part of the certification process. Because Markle was being certified as a class action on consent, in order to ensure that notice of the class action was given in the most effective manner to the members of the class, I ordered that the City produce the detailed information in advance of the discovery process.
 In its reasons, the Divisional Court said, at para. 44, that “[t]he submission by the government defendants that the deemed undertaking applies only where a party is compelled to disclose its own private information in discovery” is inconsistent with my decision in Markle. To the contrary, that submission is entirely consistent with the decision, properly understood.
 As the class actions judge pointed out in his reasons, at para. 8:
As a result of an application under the Municipal Freedom of Information and Protection of Privacy Act, R.S.O. 1990, c. M56 (“MFIPP”) a list of all 850+ potential class members is publicly available on more than one web site. Underlying this appeal is an evident concern that the appellants might misuse the opt-out information because of the earlier issues surrounding the opt-out process. The class action judge declined to continue the earlier protection order he had made arising out of those earlier issues, although in so doing he applied the stricter test for the granting of a sealing order dictated by Sierra, rather than determining whether, at that stage, a confidentiality order should be made pursuant to s. 12 of the CPA to preserve the integrity of the class proceedings.
All that the opt-out information does is permit someone to reduce the publicly known 850+ potential class members to the actual class members. Both the public and the appellants are entitled to know the identities of the class members who are advancing the claims unless a confidentiality order is made pursuant to s. 12 of the CPA.
 In any event, to the degree that any such concern might arise, s. 12 of the CPA gives a class action judge all of the authority that he or she needs to address that issue. Indeed, the section could not be more broadly worded. Section 12 reads:
The court, on the motion of a party or class member, may make any order it considers appropriate respecting the conduct of a class proceeding to ensure its fair and expeditious determination and, for the purpose, may impose such terms on the parties as it considers appropriate. If such a concern does arise, s. 12 is the proper route to be used to address it. There is no doubt that this class actions judge was well aware of the authority he had under that section as he expressly referred to it in his reasons dealing with the issues that arose over the original opt-out period. To the degree that the respondents feel that the class actions judge did not turn his mind to using that authority to address their expressed concerns regarding the lifting of the protection order, there is nothing that prevents the respondents from returning before the class actions judge to seek a remedy. That is the proper approach to take. The plain wording of r. 31.01.1 should not be distorted in order to effect such a remedy.